Headsets typically include a microphone along with one or two ear devices or earplugs which are worn over, on, or in the ears of users to facilitate electronic communications. Many contemporary headsets also include automatic noise reduction (ANR) or automatic noise cancellation (ANC) circuitry for automatically sensing and canceling significant portions of ambient noise, thereby improving user listening experience. ANC circuitry is simple in principle, but complex in implementation, with many headsets including as many six microphones (mics): two for feedback (fb) ANC, two for feedforward (ff) ANC, and one or two for picking up user voice signals.
One problem the present inventors have recognized is that while ANC headsets improve the listening experiences of users wearing them, they do little or nothing to improve the quality of the signals being transmitted out of the headset to other devices. For example, in many noisy environments, users wearing headsets with their mobile phones are typically required to manually switch their phones to a mute mode to prevent background noise from being transmitted by the phone to other phones and devices. Although this is effective in preventing the unwanted noise transmission, it often leads to gaps in communications as users who muted their phones forget to unmute them when they start speaking again. Moreover, in conference calls with many users manually muting and unmuting, the potential for communications gaps is even greater.
In attempting to solve the problem, some designers have provided circuitry that monitors the voice mic output and automatically mutes or unmutes based on comparison of the mic output level to one or more thresholds. However, the monitoring circuitry suffers from at least two problems that has inhibited its use in mobile phones. First, it consumes considerable power and thus shortens battery life. Second, the circuitry creates its own communications gaps not only because its slow reaction to speaking stops and starts, but also because it confuses external noises, for example voices of nearby people, with the user voice.
Accordingly, the present inventors have recognized a need for better ways of reducing transmission of ambient noise through ANC and other types of headsets.